The present invention relates to a system for determining whether a person or thing is authentic and more particularly to an authentication system where an input is compared against a reference by an optical correlator to determine whether the input is authentic.
Counterfeiting of money, banknotes, stock certificates, bond certificates, debit cards, credit cards, identification cards, social security cards, health insurance cards, immigration documents, transit passes, visas, auto parts, aircraft components, software, computer chips, consumer goods, to name simply a few, cost individuals, businesses, organizations, and countries billions of dollars each year. Similarly, fraud committed by people using a fake identity or the identity of another has become increasingly costly and burdensome to society.
Many technologies have been developed in response to such counterfeiting and fraud. Examples of such technologies include bar codes, magnetic strips encoded with authentication information, electronic xe2x80x9csmartxe2x80x9d cards having embedded integrated circuits that store authentication information, laser cards, and holograms. However, bar codes can easily be scanned and replicated using even the most rudimentary scanning and printing equipment. While more secure, magnetic strip readers and encoders are readily available and magnetic strip controls can be easily forged.
While xe2x80x9csmartxe2x80x9d cards are very sophisticated, their technology can also be copied. For example, their authentication information is an electronic key contained within the card that can always be broken because these cards are based on standard microcontrollers, typically of 8-bit construction, that can be reprogrammed. In addition, generic reprogrammable cards are widely available and can be used to mimic the performance of any xe2x80x9csmartxe2x80x9d card.
Laser cards suffer from similar, if not worse, drawbacks. This is because laser cards rely on technology virtually identical to the technology used to make compact discs. Thus, a laser can be used to scan the encoded surface of the card to record the key and any other authentication information that later can be easily replicated on blank laser cards.
Holograms on labels are affixed to goods, cards, tags, and other articles to provide a visual indication of authenticity. For example, holograms are commonly applied to credit cards and clothing tags so that a merchant will know by looking at the hologram that a card or article of clothing used in a purchase is not counterfeit.
Unfortunately, modern technology has rendered holograms relatively easy to copy and mass produce primarily because holograms possess limited information and are comprised of embossed surface structures. The use of redundant information dramatically decreases the complexity and security of a hologram because it decreases the amount of information stored. This is because thermal embossing techniques used to produce holograms limit the depth of their structure essentially to the surface of the label. Such thermal embossing techniques cannot produce a much more sophisticated hologram because the label material is made of many different moieties and thermal distortion during embossing limits the depth of the structure that can be embossed essentially to the surface. As a result, digital scanners and holographic copying machines can be used to scan a hologram and mass produce it rendering its security effectively meaningless. Also, the holograph embossed into the label can be hardened and then used as a pseudomaster for use in duplicating the hologram in a standard holographic copier.
Finally, since authentication of holograms is done visually, there is no statistically reliable method of verifying its authenticity. As a result, even counterfeit holograms of poor quality may pass visual inspection by a merchant. As a result of these many drawbacks it is obvious why holograms have become less and less useful as a deterrent to counterfeiting.
What is needed is a method of authentication that cannot be easily copied or replicated by a counterfeiter. What is preferably needed is an authentication method that is impossible to copy or replicate. What is also needed is a label or applique"" that can be replicated with high aspect two-dimensional or volume surface structures that can extend below its surface so as to more securely store authentication information. What is still further needed is a label or applique"" that masks the authentication information to make it difficult, if not impossible, to copy. What is also needed is a label or applique"" having these characteristics that is read by a reader that positively verifies its authenticity. What is still also needed is such a label or applique"" that can record either or both key authentication information and biometric authentication information.
An authentication system and method using an input and a reference each having a pattern made up of a plurality of pairs of phase structures that each have a size smaller than six microns and can have a size smaller than about one micron so as to make the input and reference difficult, if not virtually impossible, to copy. Either the input or the reference, or both, are comprised of phase volume masks that have the structures phase encoded or replicated therein. The authentication system includes an optical correlator that is coupled by an energy recording device to a computer that preferably includes a digital signal processing engine made up of one or more processors.
The pattern is a random pattern that preferably is a stochastic random pattern. The pattern can also include a predetermined pattern, such as a biometric pattern, that is convolved or otherwise integrated with the random pattern to scramble and hide the predetermined pattern and produce a phase convolved volume mask. Preferably, the mask can be constructed such that the pattern, whether phase convolved or not, is invisible or substantially invisible to the naked eye.
The mask preferably is of laminate construction such that the phase structures a covered by are protective filler that also impedes the transmission of short wavelength radiation, particularly X-ray radiation, to make the mask more secure. A protective layer of a relatively hard material preferably is disposed between the filler and each of the structures and serves to further protect the structures while being capable of making them optically distinct. Where the mask is for a transmission-mode correlator, the protective layer is transparent. Where the mask is for a reflective-mode correlator, the protective layer is opaque and can even be reflective.
The mask can be replicated using a master or a submaster made from the master. The master is made using a recording medium that preferably is a photosensitive material. Light from a light source, preferably a laser, is directed through an aperture containing the master pattern, such as a diffuser or another mask, onto the recording medium. To produce such small phase structures, the size of the aperture is selected to be as small as possible, preferably no more than a few millimeters, relative to the surface area of the recording medium and the master pattern is spaced a distance from the recording medium. By this novel recording arrangement, a diffuser or another mask having phase structures larger than six microns and having an aspect ratio less than 1:1 can be used to record a master having a pattern of phase structures in the recording medium that can be each smaller than six microns and can have an aspect ratio (AR) greater than 1:1, typically greater than about 2:1 and preferably greater than 10:1 or more. Preferably, each structure can have an AR greater than the above recited values and in any given phase volume mask input or reference, at least a plurality of pairs of structures have an AR greater than 1:1.
Where the mask is a phase convolved mask, the recording arrangement is similar with the exception that another mask containing the predetermined pattern, i.e. an information mask, is placed adjacent another mask containing the random pattern, i.e. a scrambler mask. The spacing between the aperture and the recording medium is selected so as to Fresnel transform the predetermined pattern and the random pattern such that they convolve together.
The master is therefore a key that can be used to directly replicate phase volume masks, some of which are used as references and others of which are used as inputs. The master can be used to construct submasters made of a metallic replica mounted to a substrate.
In turn, the submaster can be used to replicate by embossing or stamping the replica into a replicating material that has a relatively uniform molecular weight distribution so as to be able to reproduce the structures that are less than six microns in size and which can be of submicron size. Such a replicating material preferably is comprised of molecules that have a molecular weight that provides high homogeneity. The molecule of the replicating material is a polymer that preferably has one or more of the following structures: relatively long polymer chains for better thermal stability and integrity, ester and carboxyl groups to provide controlled cross-linking and high sensitivity, carbon chains having a saturated carbon for good rigidity and uniformity, alkene functional groups for minimizing shrinkage to maintain the integrity of structures of submicron size, and benzyl functional groups for providing rigidity and structural stability. One preferred replicating material is polyvinylcinnamate that is comprised of cinnamoyl chloride and polyvinyl alcohol that preferably has entrapped water molecules that function as plasticizers for prolonged mask life.
If desired, the master can be used to replicate masks by an adhesive replication process. In one preferred process, the master or a diffuser can be used to directly replicate masks. A drop of adhesive that preferably is ultraviolet light-curable is placed on a prepared portion of a substrate. The master or diffuser is placed over the adhesive such that the structures of the master or diffuser are brought into contact with the adhesive. Pressure, preferably from a roller, is applied to urge the adhesive into the voids between the structures of the master or diffuser and to squeeze out excess adhesive. Excess adhesive is wiped away before the adhesive between the substrate and master/diffuser is cured. After sufficient curing, the master or diffuser is peeled away and the formed adhesive is left to post-cure.
The correlator includes a light source, an aperture window arrangement that spaces the input and reference apart, a Fourier transform lens, and the energy recording device. Light from the source illuminates the input and reference producing pattern images that are Fourier transformed on the lens to produce a joint power spectrum at the output plane of the lens that has interference fringes.
The interference fringes are recorded by the energy recording device and the resultant image is electronically captured by a capturing device that preferably is a frame grabber. The image is processed by the computer preferably by first nonlinearly transforming the image before an inverse Fourier transform is performed. Such a correlator is a nonlinear joint transform correlator.
Where the input and the reference lie on different planes, such as where the input is carried by a box or other object remote from and exteriorly of the correlator, a quadratic term, i.e. a chirp, is encoded in the resultant image. This quadratic term is resolved by determining the two planes in which the quadratic phase modulation is zero to thereby locate the planes where the critical cross-correlation terms appear. Once the planes are located, the cross-correlation terms are ascertained and then used to determine the presence or absence of the correlation spot or spike.
To produce a correlator that is invariant to rotation, i.e. invariant to the case where the input is rotated relative to the reference, a circular correlation is performed. To produce a correlator that is invariant to illumination, the electronic image of the joint power spectrum containing the interference fringes is nonlinearly thresholded.
In one preferred correlator embodiment, either or both the reference and the input can comprise a spatial light modulator (SLM) that preferably is a liquid crystal panel having an array of pixel phase elements, each of whose phase can be selectively varied. The SLM is operably connected to a computer that can be in communication with a database of phase patterns that can be quickly downloaded to the SLM for comparison with inputs or references of many different kinds, classes or families.
Where the input is a phase convolved mask and the reference is an SLM, the computer can download to the SLM reference the random pattern, i.e. the scrambler mask, as well as the predetermined pattern, i.e. the information mask, that are both displayed by the SLM. If desired, the SLM can be coupled to a scanner that can scan, in real time if desired, a pattern that is used as the predetermined pattern or information mask. In this instance, the random pattern or scrambler mask is downloaded to the SLM from the computer. Such a scanner can comprise, for example, a scanner that scans biometric information of a person, such as a fingerprint, facial image, voiceprint, retina pattern, iris pattern or the like.
In another preferred correlator embodiment, the correlator is equipped with an optical scanner assembly that directs a portion of the light from the source onto an input that can comprise a phase volume mask that is part of a label on an object that can be a tag, label, box, or the product itself. As a result, the input is located on a plane different than that of the reference. Light in the form an image or pattern is reflected from the input returns to the scanner assembly where it is correlated with that of the reference to determine whether the input is authentic.
In a still another correlator embodiment, the computer controls access through a door depending upon whether the input is authentic or not. A door opening device is operably connected to the computer. Opening of the door is prevented if the input is not authentic and is permitted if the input is authentic.
In one preferred compact correlator embodiment, the correlator has a housing preferably of block construction with a light tunnel that preferably is generally U-shaped. The light source is disposed at or adjacent one end of a first leg of the tunnel and directs light toward a pair of aperture windows at the opposite end of the leg that hold and space apart the input and reference. A collimating lens and beam splitter are disposed between the light source and the aperture windows. The images reflected from the input and mask is directed through a Fourier lens in a middle leg of the tunnel toward a mirror that reflects the images the recording device, located at or adjacent one end of a third light tunnel leg.
In another preferred compact correlator embodiment, the light source is located onboard the housing and inboard of the other components of the correlator including a parabolic mirror that directs light from the source toward the aperture windows to illuminate the input and reference. The light source preferably is acutely disposed relative to the mirror at an angle between about 30xc2x0 and about 60xc2x0 that preferably is about 45xc2x0. The recording device preferably is located on board the correlator housing.
In a still further preferred compact correlator embodiment, the light source and recording device are both located on-board the housing with the light source disposed generally transverse to the recording device.
Objects, features and advantages of the present invention include a correlator of compact and low cost construction that is well suited for commercial use, that uses a high-aspect ratio surface relief phase or volume mask that is highly secure in that it cannot be easily copied, that uses such a mask that can be quickly and easily recorded and which can be cheaply replicated in mass quantities as labels that can be quickly and easily applied to cards, tags and other objects; that uses masks that are resilient, durable, rugged, and long-lasting; that can use real-time biometric information to verify the authenticity of the input; which is versatile in that it can correlate an input that is located in a different plane than that of the reference or which is rotated relative to that of the reference; and which is a correlator that is flexible, rugged, durable, resilient, lightweight, and quick and easy to manufacture.
Other objects, features, and advantages of the present invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.